This study analyzed data from the Korea National Health and Nutrition Examination Survey (KNHANES), a cross-sectional, nationally representative survey conducted by the Korea Centers for Disease Control and Prevention from 2012 to 2017. The survey used a stratified multistage probability sampling design to draw a sample representative of the entire South Korean population. The KNHANES included health interviews, health behavior surveys, nutrition surveys, and health examinations.

Of the 47,283 participants enrolled in the KNHANES between 2012 and 2017, we included those aged 12‐18 years (n=3702). Participants with missing parental (n=252), mental health (n=320), or parental smoking (n=369) variables were excluded. Finally, we examined the data of 2761 adolescents enrolled in the KNHANES (Figure 1).

We used the SAS survey procedure (version 9.3; SAS Institute Inc) to run a complex sample design and analyze the survey data. Mean and SE values were used to represent continuous variables, and mean percentage and SE values were used to represent categorical variables. We used an ANOVA and the chi-square test to compare the baseline characteristics and mental health variables of adolescents and parents. Subsequently, we performed multiple logistic regression analyses to evaluate the association between adolescents’ mental health variables and differences in parental smoking status. We examined the odds ratios (ORs) and 95% CIs after adjusting for age, sex, smoking status, alcohol consumption, and household income. In addition, we examined the ORs and 95% CIs in the association between adolescents’ mental health and mothers’ current smoking status and cognitive stress.

The original data for the KNHANES were collected after being approved by the institutional review board of the Korea Centers for Disease Control and Prevention. Written informed consent was obtained from all participants prior to the original data collection. As this study is a secondary analysis using publicly available and deidentified data, it was determined to be exempt from a separate institutional review board review (number 1041078-202106-HRSB-172-01). No compensation was provided to participants for this specific analysis.

Table 1 shows adolescents’ mental health according to their baseline characteristics and mental health variables, along with those of their parents.

Regarding adolescents’ cognitive stress, we found significant differences according to their age (P=.02), sex (P=.005), current smoking status (P<.001), and heavy drinking status (P<.001); maternal age (P=.03), current smoking status (P=.006), and cognitive stress (P=.001); and paternal age (P=.04) and diagnosis of depression (P=.01).

For adolescents’ experiences of melancholy, we observed significant differences according to their age (P=.007), sex (P<.001), current smoking status (P=.001), and heavy drinking status (P<.001), as well as maternal current smoking status (P=.009) and cognitive stress (P<.001). No significant associations were found for the paternal variables.

Suicidal ideation showed significant differences according to adolescents’ sex (P<.001), current smoking status (P=.003), and heavy drinking status (P<.001); maternal education level (P=.02), current smoking status (P=.02), and cognitive stress (P=.002); and paternal heavy drinking status (P=.046).

Table 2 presents the association between adolescents’ mental health and maternal smoking status. In Model 1 of the logistic regression analysis, we adjusted for adolescent age and sex. In Model 2, we adjusted for adolescent age, sex, smoking status, alcohol consumption, and household income. The analysis revealed that maternal smoking status was significantly associated with adolescents’ cognitive stress and melancholy (P=.03). The ORs for adolescents’ cognitive stress were 1.72 (95% CI 1.08‐2.75) and 1.63 (95% CI 1.04‐2.59) in Models 1 and 2, respectively, in the group with mothers who were ex-smokers; the ORs were 1.88 (95% CI 1.20‐2.95) and 1.65 (95% CI 1.06‐2.56) in Models 1 and 2, respectively, in the group with mothers who were current smokers. The OR for adolescents’ experience of melancholy was significant in Model 1 at 2.09 (95% CI 1.20‐3.65) only in the group with mothers who were current smokers. In addition, the OR for adolescents’ suicidal ideation was significant in Model 1 at 2.39 (95% CI 1.17‐4.88) only in the group with mothers who were current smokers. Paternal smoking was not significantly associated with adolescents’ mental health.

Figure 2 shows the association between adolescents’ mental health and mothers’ current smoking status and cognitive stress. We classified mothers into 4 groups depending on their current smoking status and cognitive stress: Group A (reference group) for mothers who were “not current smokers and without cognitive stress,” Group B for mothers who were “not current smokers but with cognitive stress,” Group C for mothers who were “current smokers but without cognitive stress,” and Group D for mothers who were “current smokers with cognitive stress.” The significant ORs were 1.36 (95% CI 1.06‐1.75) in Group B and 2.09 (95% CI 1.12‐3.90) in Group D for adolescents’ cognitive stress, and 1.59 (95% CI 1.11‐2.27) in Group B and 2.27 (95% CI 1.10‐4.71) in Group D for adolescents’ experiences of melancholy.

However, adolescents’ suicidal ideation was significant for only Group D (OR 2.74, 95% CI 1.21‐6.23). Figure 2 shows that adolescents’ mental health ORs in Group D (current smokers with cognitive stress) were higher than those in Group A (reference group).

This study examined the association between parental smoking status and the mental health of their adolescents in South Korea, specifically focusing on cognitive stress, melancholy, and suicidal ideation. Furthermore, we analyzed these factors separately for mothers and fathers to identify any differences in the effects.

We observed a significant relationship between adolescents’ cognitive stress and their parents’ age and current smoking status. As parents age and their physical aging progresses, their employment stability may decrease; in addition, they often have to care for their own older parents. This can expose their children to various stressful situations [21]. In addition, mental health problems such as parental depression can negatively affect children’s cognitive health. However, strengthening protective factors across various areas of adolescents’ lives may help prevent psychological health problems among adolescents [22]. Therefore, researchers should use multiple approaches to improve parental mental health and reduce perceived stress among adolescents.

Mothers’ current smoking status and cognitive stress influenced their adolescents’ experiences of melancholy, whereas fathers’ smoking status had no such significant effect. Parent–child communication is related to adolescents’ life satisfaction, with their relationships with mothers having a particularly strong influence on girls [23]. In contrast, adolescent aggression and depressive symptoms were associated with increased mother-adolescent conflict [24]. In South Korean culture, the mother-child relationship is notably close [25], which may explain why mothers have a stronger influence on their adolescents’ mental health than fathers. The observed effects of maternal smoking could also be influenced by prevailing social norms. In many Asian cultures, women who smoke may be perceived as violating traditional norms, leading to moral judgments (eg, viewed as less respectable, lacking self-control, or not family-oriented). This social stigma can indirectly affect adolescents’ mental health through social pressure, family reputation concerns, or community gossip.

Reiss et al [26] analyzed data from the German National Health Interview and Examination Survey for children and adolescents, revealing that children of parents with higher education levels had fewer mental health problems in response to stressful life situations than their peers. Moreover, Guerrero et al [27] reported that the children of parents with lower education levels required interventions to address their risk of developing mental health problems due to stressful situations. These results echo those of our study, as parents’ level of education can create high expectations for their children to study or go to school. In addition, the expression of conflict can be attributed to differences in one’s future goals.

Maternal smoking and cognitive stress consistently had significant effects on adolescents’ mental health, as mothers’ smoking status was associated with their adolescents’ cognitive stress, melancholy, and suicidal ideation. Adolescents whose mothers were current smokers and experienced stress exhibited higher cognitive stress, melancholy, and suicidal ideation than those whose mothers did not smoke or experience stress. Amrock and Weitzman [28] analyzed data from the National Health Interview Surveys in the United States to examine the mental health of children aged 4‐17 years and identified a negative effect of parental mental health and sex on adolescent mental health. However, our study found that only maternal cognitive stress significantly affected adolescents’ cognitive stress, melancholy, and suicidal ideation. This could be because in South Korea, mothers are primarily responsible for raising their children; thus, their mental health may have a more significant influence on their children than that of their fathers. Moreover, in a study comparing mothers’ child-rearing stress in the United States and South Korea, South Korean mothers showed substantially higher stress levels than did American mothers [29].

Lee et al [30] found that adolescents’ mental health was significantly associated with maternal mental health and smoking status but not with paternal mental health. This difference may be because fathers often display cooperative and constructive problem-solving behaviors that adolescents tend to emulate. However, their focus on problem-solving may reduce emotional engagement, making interactions feel less supportive than the warmth typically provided by mothers [31]. Moreover, maternal depression can impair mother-child attachment and elevate maternal stress, leading to diminished nurturing behaviors. This creates a stressful home environment, potentially resulting in developmental challenges and emotional difficulties for adolescents [32]. Children may develop psychological symptoms as a result of receiving insufficient support during challenging moments, thereby necessitating the consideration of parental mental health [33]. By addressing parents’ needs through family support programs, health professionals can improve the mental and behavioral health of adolescents as well as the happiness and nurturing nature of parents. Such family support programs can be a part of treatment and prevention [34].

Stress is a significant risk factor for smoking, as individuals often smoke to reduce stress [35]. In South Korea, the negative perception of women smoking likely means that the actual number of female smokers is substantially higher than the officially reported smoking rates [36]. Therefore, women may be more likely to smoke in personal spaces, such as their homes, than in public areas; therefore, children may be more likely to be exposed to their mothers’ smoking.

Our findings provide valuable evidence supporting the influence of parental smoking on adolescents’ mental health. However, this study has some limitations. First, our cross-sectional design limits causal interpretation. We analyzed data from the nationwide KNHANES; therefore, the results are associative rather than causative, restricting our ability to confirm causal relationships between parental smoking and adolescent mental health outcomes. Second, this study focused exclusively on South Korean adolescents and parents; therefore, the results may not apply to populations in different cultural or social environments, and their generalizability may be limited. Finally, the accuracy of self-reported parental smoking status remains a potential issue. The cultural stigma surrounding women engaging in smoking in South Korea may lead to the underreporting of mothers’ smoking behaviors. Future research should consider a wider range of variables and interaction effects to provide a more comprehensive analysis of the factors affecting adolescent mental health and strengthen the understanding of these relationships across cultural contexts. In addition, future studies should incorporate longitudinal data to better understand the causality of these variables.

The cross-sectional design of our study limits the ability to establish causality, while the self-reported nature of data presents a risk of underreporting, especially for maternal smoking due to cultural stigma. We recommend that future research use longitudinal data to better understand the causal relationships between variables. In addition, we suggest incorporating diverse measurement methods and standardized mental health scales to overcome the limitations of single-item, self-reported data.

We examined the relationship between parental smoking status and the mental health of adolescents in South Korea and found a significant association between adolescents’ mental health and mothers’ current smoking status. Moreover, maternal stress has a substantial association with their adolescents’ well-being. We recommend programs to support mothers in managing their stress without having to rely on smoking and to quit smoking, as this can lead to improvements in their children’s mental health. Therefore, systematic support at the national and domestic levels is required. Future research should explore additional factors affecting both parents’ and adolescents’ mental health.